Abstract 043: Local Passive Heat in the Treatment of Nocturnal Supine Hypertension in Autonomic Failure

Abstract

Supine hypertension affects about half of patients with primary autonomic failure (AF), complicates the treatment of orthostatic hypotension (OH) and induces nocturnal polyuria, resulting in worsening of morning OH. We previously showed that short exposure to local passive heat (40-42°C applied for ≤2 hours over abdomen and pelvis with a heating pad) acutely decreased systolic blood pressure (BP) by -25±5 mmHg in AF patients with supine hypertension due to decreases in stroke volume (-29±5%) and cardiac output (-30±5%). In this study, we hypothesized that local passive heat therapy applied overnight would lower nocturnal BP and polyuria, and improve early morning OH in these patients. Ten AF patients with supine hypertension (age 76±2 years, 6 men, supine systolic BP 168±3 mmHg) received passive heat (38°C with a water-perfused heating pad placed under the torso) or placebo, in a 2-night crossover study. Supine BP was monitored every 2 hr from 8pm-8am. Heat therapy was applied from 10pm-6am. Morning orthostatic tolerance was assessed at 8 am. Systolic BP significantly decreased during overnight heat therapy compared to placebo (Figure; P<0.01 by mixed-effects model) with a maximal reduction of 30±6 mmHg at 4 hours of heat. Despite lowering nighttime BP, heat therapy did not decrease nocturnal diuresis or improve morning OH. In conclusion, low levels of local heat therapy applied overnight effectively lowers BP in AF patients with nocturnal supine hypertension. Thus, local heat therapy offers a novel non-pharmacologic approach to treat this condition, but future studies are needed to assess the long-term safety of this approach.